Gallium Nitride high electron mobility transistors (GaN HEMT) have many advantages, such as high voltage resistance, low channel resistance and high electron drift velocity, etc., so can be applied to high-speed switching devices and high-power devices. The transistor devices can form high-concentration two-dimension electron gas (2DEG) and improve the transmission characteristics, which can obviously better the output current density and the on-resistance thereof. However, the transistor devices tend to be normally on because of high-concentration two-dimension electron gas, so usually cannot be applied to enhancement mode or normally-off transistor devices. Thus, the application of the transistor devices is limited.
Enhancement mode transistor devices are more easily integrated into microwave circuits and logic circuits, and can save more energy. Currently, major enhancement mode transistor devices include recessed gate transistor device, p-(Al)GaN epitaxial layer transistor device and F− Ion implant transistor device, etc.